For example, JP-A-2016-035238 (PTL 1) is known as a blower equipped with a resin-made centrifugal fan, and particularly as a blower for an air-conditioning system for a vehicle.
This type of blower for an air-conditioning system for a vehicle includes: a resin-made fan body; a motor; and a rotation prevention member (stator) in which a rotating shaft of the motor is inserted and which is fitted in a boss formed at the rotation center of the fan body. The rotation prevention member is made by injection molding of resin and has a shaft hole, and the rotating shaft with a round-bar shape (with circular cross section) is press-fitted in the shaft hole. Thereby, the rotation prevention member can transmit the torque of the motor to a centrifugal fan without running idle with respect to the rotating shaft.
In addition, the rotation prevention member is provided in its outer circumference with a concave part to be fitted to the boss and, once this member is press-fitted on the rotating shaft, a large-stress generation part where large stress is generated with the concave part as its point of origin and a small-stress generation part where smaller stress than that of the large-stress generation part are formed.
Further, in the rotation prevention member, a weld face (weld line) which is easily broken by stress is formed in a portion where two flows of resin meet during the process of injection molding.
Thus, PTL 1 states that a weld face is formed at the location of the small-stress generation part, which makes it possible to prevent a crack from being generated in the portion where the weld face is formed even if the rotation prevention member is press-fitted on the rotating shaft and uneven stress is generated.